This presentation will highlight how maternal sleep plays a role in both maternal health as well as fetal wellbeing. Data will be presented to show that sleep offers a modifiable risk factor to improve pregnancy outcomes.
Dr. Louise O’Brien earned a bachelor’s degree with honors in physiology from the University of Leeds, United Kingdom in 1992. In 1998 she gained a Ph.D. in physiology from Keele University, United Kingdom. After completing post-doctoral work in maternal and infant health research, Dr. O’Brien relocated to the United States in 2001 to train in pediatric sleep research. She completed a post-doctoral fellowship in pediatric sleep research at the University of Louisville, KY. In 2006 she was recruited to the faculty at the University of Michigan as an Assistant Professor Dr. O’Brien also holds an appointment as an Assistant Research Scientist in the Department of Oral & Maxillofacial Surgery.
Dr. O’Brien has unique expertise and is one of very few researchers actively investigating the impact of sleep-disordered breathing on adverse pregnancy outcomes such as pre-eclampsia in the mother and growth retardation in the fetus. Since her arrival at the University of Michigan, Dr. O’Brien has built collaborations between the Sleep Disorders Center and the Department of Obstetrics and Gynecology and has several active studies. She has published over 40 original manuscripts and over a dozen invited reviews and book chapters. In addition, she is an ad hoc reviewer for NIH study sections and for 16 professional journals, including the American Journal of Respiratory and Critical Care Medicine, Archives of Disease in Childhood, International Journal of Gynecology and Obstetrics, Pediatrics, Sleep, and Sleep Medicine.
Dr. Warland has disclosed that she does not have any real or perceived conflicts of interest in making this presentation.
This presentation was part of the Stillbirth Summit 2021. This individual lecture will be awarded .5 hours of continuing education credit to include viewing the lecture and completing evaluation and post-test. Once received a certificate will be emailed to the address you provide in the post-test. If you did not register for the Summit WITH Continuing Education, you can purchase the continuing education by clicking here. This purchase will provide you access to all Stillbirth Summit 2021 lectures including continuing education credit. There is no charge for viewing the presentation.
Latifa Hamilton: Dr. Louise O’Brien is an Associate Professor at Michigan Medicine, who has unique expertise in the field of sleep in maternal, infant, and child health research. She holds a BS in human physiology from the University of Leeds, a PhD in neonatal physiology from University of Keele, postdoc degree in maternal and infant research from North Staffordshire Hospital, fellowship in pediatric sleep from the University of Louisville, and an MS in clinical research design and biostatistics from the University of Michigan.
Dr. O’Brien’s main focus is the impact of sleep disruption, clinical sleep disorders, and sleep behaviors on adverse maternal and fetal outcomes and how sleep-focused interventions can reduce the burden of poor pregnancy outcomes. Her presentation today is titled, The Influence of Sleep on Maternal and Fetal Wellbeing. Let’s all welcome Dr. Louise O’Brien.
Dr. Louise O’Brien: Thank you for that introduction, and thank you to the Star Legacy Foundation for inviting me to speak today about how maternal sleep influences both maternal and fetal wellbeing. I’m going to talk about various sleep disorders or sleep behaviors as you can see on this slide. We’ll talk about the first few first, and at the second half of the talk I’ll go through sleep position.
The first one is sleep-disordered breathing. This is a really common clinical sleep disorder, otherwise known as sleep apnea. Essentially sleep-disordered breathing is an umbrella term. At one end of the spectrum, we have habitual snoring. At the other end of the spectrum, we have obstructive sleep apnea, which is this severe form of sleep-disordered breathing.
This image is a few minutes of recording from an overnight sleep study. We have the EEG of the brainwaves in black at the top where, we have ECG of the heart rate in red, and down here where the flat lines are, this is actually an airflow coming out the nose and the mouth. Then these breathing movements are chest wall movement, abdominal wall movement, and at the bottom, we have oxygen levels in red.
What’s happening here is somebody is having an obstructive apnea. They’re trying to breathe. You can see the chest and abdominal wall is moving, but there’s no air flow. There’s a flat line. There’s nothing coming out of the nose and the mouth. At the same time, the oxygen levels are going down. Then what happens is the brain wakes up, the person takes a big gasp, gets that air in, and then off they go again, they’re starting to obstruct again. This goes on over the course of several hours during the night.
The severity of sleep apnea is marked by the apneas and hypopneas, the number per hour of sleep, which is the AHI. Less than five of these events per hour is actually normal in an adult. 5 to 15 is mild sleep apnea, 15 to 30 is moderate, and above 30 times per hour of sleep is severe sleep apnea. We’ll talk about this a little later on.
How common is habitual snoring or sleep apnea in pregnancy? You can see from this figure that in early or pre-pregnancy, we’ve got somewhere between 4 and 10% of women will habitually snow. What you can see is that in the third trimester, it significantly increases up to about a third of women. In fact, women that have preeclampsia, the vast majority, 85% of women have habitual snoring if they have preeclampsia. The frequency comes down in the postpartum period, but not many studies have looked at that. There’s only a couple highlighted here on the graph, but not to baseline levels, probably because of the weight retention that women still have.
In terms of objective measures by sleep study of obstructive sleep apnea, not many studies are out there, but we believe about 8 to 10% of pregnant women in general have sleep apnea, and of course it goes up as women are more and more overweight or they have other conditions such as the hypertension, I just mentioned. In a sample of 181 women, about half of whom were obese, that had sleep studies, what we’ve found is that compared to those with a normal BMI, so a BMI less than 25, as you go up the BMI ranges, the odds for having sleep apnea increase. Overweight women have a seven times higher odds of sleep apnea than normal weight women. Obesity class I is 12 times odds. Then once you get up to obesity class II and III, which is above 35 and 40 of the BMI, it’s about 30 times higher that, the odds of sleep apnea. It’s a very common sleep condition.
Strong link between sleep-disordered breathing and pregnancy and maternal outcomes, such as preeclampsia, gestation hypertension, gestation diabetes, and having a caesarian section. You can see here, this is a metanalysis where they’ve pooled a number of studies, 35 to 43 studies in this analysis. In the millions of participants, these are quite robust numbers, and the odds of having one of these maternal outcomes ranges from about 1.5 to about 2.8. That’s statistically significant, you can see from that chart.
It’s not just the sleep-disordered breathing. Seep duration is also related to maternal blood pressure. You can see here short and long sleep duration are measured by the red and the green colors respectively across the trimesters. We’re looking at blood pressure or adjusted mean arterial pressures in this case. You can see that in early and mid-pregnancy, no real differences in blood pressure with regards to how long somebody sleeps. But once we get into the third trimester, you can see a U shape starting to appear when those extremes of sleep duration have the highest blood pressures.
Sleep duration is also linked to glucose levels and risk of gestational diabetes. Again, a U shape is appearing where you’ve got those who sleep the least, or the longest have the highest glucose levels and the highest risk for development of gestation diabetes. Indeed, those women who have very short sleep durations and less than four hours are five and a half times more likely to develop gestational diabetes. One study has actually shown that for every hour of reduced sleep time, it’s linked with a 4% increase in glucose levels on those oral glucose tolerance tests.
Again, it’s not just a duration, even timing matters. Even if you have optimal sleep, and for an adult, it’s about seven to eight hours. Even if you have optimal sleep, but your timing is off. Maybe you have eight hours, but you have it from two in the morning till 10 in the morning, that still matters. If you look at studies of sleep midpoint– now midpoint is halfway between sleep onset and wake time. It’s that bit right in the middle. We see from the non-pregnant literature that that is associated with poor cardiometabolic outcomes.
In this figure, this is data taken from an actigraph. This is a wrist-worn medical grade device. It’s much more accurate than the wearables that you can buy off the shelf. Every row is a day. In this case, we start Wednesday, the 24 hours here, Thursday, and so forth. The black is activities. This is when somebody is active and moving around. The yellow is light exposure. Maybe they’re outside, maybe they’re inside in a brightly lit room. Then the blue is sleep. What I’ve done is I’ve marked the midpoints or the approximate midpoints of sleep on this graph.
You can see that this person is pretty stable with bedtimes except on the weekends, they go to bed a bit later and get up a bit later. In pregnancy, we’re starting to learn that the midpoint of sleep matters in terms of pregnancy outcomes. If that midpoint is shifted to after four o’clock in the morning, so people are pushing asleep later and getting up later, we see the latest sleep midpoint is linked with an increase in gestational diabetes, an increase in preterm birth and that’s even if seek duration is optimal at seven to eight hours.
Poor sleep quality. Very common in pregnancy. Between 70 and 80% of women will endorse poor sleep quality. What we found in a large study is that a small but meaningful proportion of women, 14%, actually had frequent use of something to help them sleep. Frequent, meaning at least three nights out of the seven. If you look at that list, you can see that 9% of women were endorsing taking pain medications to help them sleep. Even one and a half percent of women were endorsing that they drink alcohol to specifically help them sleep. This is certainly a problem.
We also know that poor sleep quality itself is associated with a one and a half to two times odds of the development of gestation diabetes, and importantly although not the focus of this talk is poor sleep quality and insomnia in pregnancy or in the postpartum period are very tightly linked with depressive symptoms.
There’s actually a disproportionate burden of sleep disturbance in Black women. Sleep disturbances have a high prevalence and often greater severity in Blacks compared to whites, and that’s in the general population. We believe that this contributes to greater cardiovascular morbidity seen in people of color. In the pregnancy literature, non-Hispanic Black women have double the odds of poor perinatal outcomes compared to white pregnant women.
In a study that we did in Detroit, we found that Black pregnant women have a much higher prevalence of short sleep duration, worse sleep quality, more insomnia symptoms, and have a harder time falling asleep compared to whites. Indeed the burden of sleep disturbances such as snoring, restless leg syndrome, insomnia symptoms, excessive daytime sleepiness is much higher in Black women, and we can see from this figure that a large proportion of Black women, so 25% have at least five at the sleep-wake disorder. This is layer upon layer of sleep problems which is a big burden and how does that relate to poor pregnancy outcomes in this population.
In this figure here, we’re looking at the proportion of babies who were born preterm. This is divided into European American women, African-American women, and then further divided into those who are good sleepers, and those who are poor sleep. This is poor sleep quality and good sleep quality. What you see is in the European American women, it didn’t really matter whether they were good or poor sleepers. The proportion of preterm births was about the same, but that was not the case for the African-American women, where the proportion of preterm birth was 10 times higher in those African-American women who endorsed poor sleep quality compared to those with good sleep quality.
Other work has shown that Black women appear to exhibit a large inflammatory response than whites at the same level of poor sleep, which suggests that maybe there’s an enhanced physiological response and this other work has supported that. Now, when we’ve done studies in Ghana, we have failed to find any association between these sleep problems and preterm birth, cesarean deliveries, low birth weight, NICU admission, or stillbirth.
There’s not much out there actually looking at racial disparities in sleep in pregnancy. That’s an area that’s quite active investigation right now, but there are some thoughts, and Green in 2014 had said, “Being a Black woman in the United States appears to increase the risk for adverse birth outcomes.” Why is that? That’s something that is under heavy investigation right now.
Does maternal sleep impact the fetus? Well, we know that fetal growth in women with sleep-disordered breathing appears to be altered. We have multiple studies that are showing fetal growth restriction. This is the one that we did quite some time ago now, where we showed that compared to women who were non-snorers, women who were habitual snorers, if they started their snoring symptoms during pregnancy, they didn’t seem to have any difference in the birth centile of the baby. But if they had had these symptoms longer, so they entered pregnancy with habitual snoring, those babies were born smaller.
Also, if you look at objective data with the severity of the sleep apnea going from no sleep apnea, all the way through mild, moderate, severe sleep apnea, the proportion of babies born small was increasing as the severity of sleep apnea got worse.
There’s also a couple of studies that have come out to say, “Well, actually, maybe the other end of the spectrum is true as well, is that babies are born large for gestational age and it could be related to the underlying mechanisms that are going on.” I believe that there are different mechanisms and that there are a proportion of babies that are born small, and there are some babies that are born large for gestational age. Certainly, fetal growth is impacted.
This was a small study out of Australia that did objective sleep studies in 14 pregnant women with sleep apnea and 27 women that did not have sleep apnea. What they found was there was no difference in the birth centile. No difference. Those babies were born right around the 50th centile.
They’d also take an ultrasound of fetal growth at 32 weeks, and when they looked at that ultrasound measure and drew a line from 32 weeks down to the birth centile, they saw that some of these babies were actually falling across the fetal growth curve. When they looked a bit closer, they realized that actually it was the women with the sleep apnea. Those babies were much more likely to fall across the fetal growth curve, even if they were still born within normal limits and would not be classified as growth restricted. This makes the point of maybe one measure of delivery is insufficient to really get at what’s going on.
We’ve done a study where we’ve taken serial growth measure. We take at least three growth measures during pregnancy, and then the delivery measure on 54 women that were negative for sleep apnea on sleep study, 34 women who had sleep apnea but were not being treated, and 14 women who were treated with positive airway pressure during pregnancy.
What we found after we’d accounted for other reasons why these babies both may be a little different, we found that women who had untreated sleep apnea had a threefold increase in the odds of fetal growth problems. Meaning that the baby’s growth was falling across the growth centiles as the gestation progressed. Yet, in women who were treated with the positive airway pressure, there were no differences in the fetal growth between those treated ladies and the ones who had no sleep apnea at all. This makes us wonder if application of positive airway pressure could actually help the baby grow a little better.
We’ve also done a fetal heart rate monitoring at the same time that we’ve done home sleep study. You can see here, this is the monitor. We’ve put this on multiple women now, and we’ve sent them home with a home sleep test. For this particular project, we were interested not just in associations, but in temporal relationships. Meaning, within 30 seconds or 60 seconds of the mother’s respiratory efforts or having respiratory events, what was the baby’s heart rate doing?
In this study, we’ve got 41 third trimester women, about half that had sleep apnea, and we found that 18 fetuses had late fetal heart rate decelerations. There was a total of 37 of these decelerations of 18 women, and 84% of the majority were temporarily linked to a maternal respiratory event. These things were happening within 60 seconds of the maternal respiratory event. The baby’s heart rate was responding to something.
In fact, when we looked at these women for prolonged decelerations, we found that six women had a total of 10 prolonged fetal heart rate decelerations. You can see the average length of time, about four and a half minutes. When we went back to look at that overnight sleep studies, we found that all of them actually had sleep-disordered breathing in the moderate range. 90% of those prolonged decelerations were temporarily linked to a maternal respiratory event. Something was happening with the mom’s breathing, and the baby’s fetal heart rate was responding.
What about treatment of sleep-disordered breathing in pregnancy? Not a lot is known actually, but typical treatment, as I mentioned before, is positive airway pressure. We know that it reduces blood pressure in non-pregnant women and adults, but we don’t know much about it in pregnancy. The studies that have been done, you can see that all the sample sizes are really, really small.
What you’re looking at here on the left is systolic blood pressure, diastolic blood pressure on the bottom. Very small samples. There’s a blue group, which is a standard of care control group. There’s a red group, which is standard of care plus positive airway pressure. The sample size were seven and nine, I think, in each of these arms. This is weeks of pregnancy along the x-axis and basically looking at blood pressure trajectories in each of these two groups.
Nothing much happened until about 30, 31 weeks. That’s when the control blood pressure start to be statistically significantly higher than the intervention group. You can see here that this is going up while the red group is staying stable or coming down, this is the CPAP group was the same for systolic and diastolic blood pressure. What’s really interesting about this is that the anti-hypertensive medication doses were going up in the standard of care blue group, but they were staying stable or coming down in the CPAP group. Again, what is it about CPAP that’s working here?
These four figures are from a case report showing a lady with preeclampsia, showing her blood pressure and some other angiogenic markers of preeclampsia. Where the red line is here, this is where the CPAP was started. You can see her blood pressures were going up, the CPAP was started here, and then her blood pressures stabilize and start to come down until a couple of weeks later when they start to track higher. If you look at these three other panels of androgenic markers, you see the same pattern. They seem to stabilize or come down in the week or two after the CPAP application, but then they start to track up. What the author said was we seem to be able to at least help this woman stay pregnant for several more weeks and help that baby gain some extra weight.
What about fetal movement? In this figure, you’re looking at the number of fetal movements across the maternal sleep. Hours of maternal sleep is on the X, the number of fetal movements per hour of maternal sleep are on the Y. Healthy pregnancy is the dark bars. You can see this is what is typical across the night. In the gray bars, this is a woman with preeclampsia. We’d expect that maybe the baby moves a little less, and certainly we can see that the number of movements across the night are certainly much lower.
Then when we give that preeclamptic woman CPAP, we see that the baby’s movements come back again. They don’t come back to what we possibly need at more typical levels, but they certainly are coming up from what they were without the CPAP. Why is this? We really don’t know, but again, it’s more evidence that’s accumulating that CPAP could potentially help some of these babies.
In terms of infant outcomes, we have a study where we’ve given APAP to about 45, 48 high-risk pregnant women. These were hypertensive pregnant women. We found that this was associated with improved birth weight. These babies were born a bit bigger, even after we’d accounted for how long the women had used the CPAP or the autotitrating positive airway pressure. It was also linked with longer gestation. We kept these women pregnant about two and a half weeks longer than the women who did not use the positive airway pressure. Also, their blood pressure did better. They felt better, the affect was better, and the women themselves reported that they could feel their babies moving more when they were using the positive airway pressure.
I’ll share a couple of cases with you. This was a lady who had a poor obstetric history. She had two fetal demises at 20 weeks and 19 weeks, respectively, and a premature delivery at 27 weeks, all due to sudden onset preeclampsia. She presented again with her fourth pregnancy. Her obstetrician actually called us and asked if she could be in this trial. We enrolled her at 21 weeks. She did not have sleep apnea, she did not have hypertension, and she was very adherent to a positive airway pressure. She used about seven to eight hours every night. She used it across pregnancy. She did not develop preeclampsia this time, and she delivered a healthy male baby at 36 weeks. That was the first time that she’d walked out of the hospital with a baby.
The placenta, we looked at that, it was normal this time, very unlike the previous placentas that were typical for preeclampsia, except for one small infarct, which looked like it could potentially be more preeclamptic looking. Was this because we’d given her APAP? We don’t know, but we’d like to think that this certainly helped her pregnancy.
This lady was more typical of the ladies that we had in the study. She’s a 34-year-old African-American. She had gestation hypertension, a BMI of 42. This was her first pregnancy, high blood pressures when she enrolled in the study. We gave these women a sleep study on the first night, and then we started them on their positive airway pressure on the next night. What happened was, after she’d had her baseline sleep study, the morning after, before we’d even seen what her sleep study results were, she presented in triage with non-reactive fetal heart rate, reduced fetal movements, and severe maternal descents.
The plan was to deliver her that day when she presented, but one of the residents had the foresight to page us and just let us know that one of our study participants was in triage, and after some discussion, we decided to start the positive airway pressure immediately. It was ten o’clock in the morning. While that was all getting settled, I went back and I looked at her sleep study from the night before, and she had severe sleep apnea. She was stopping breathing 117 times per hour. That’s pretty bad.
When she was wearing the positive airway pressure, the fetal heart rate became reactive, the maternal stats became normal. Her blood pressures were doing great, even though she was still on the meds, and she ended up being discharged and she continued that pregnancy for another week. Her obstetrician told her to use the positive airway pressure even if she napped. “Just please use it every time you want to fall asleep,” even though this was a research device. She did, and she ended up delivering a healthy baby born.
Now we’ll move on and talk about sleep position. Just an illustration, when women are lying in the supine, on their back position, you can see here that especially the large gravid uterus, the aorta gets somewhat compressed. If you lie on side, you can see how these vessels open up. You can see how there’s an impaired uterine perfusion going on when you’re sleeping on your back.
There are several case-control studies now and a cross sectional study that have all demonstrated an association between maternal self-report of going to sleep in the supine position, and third trimester stillbirth. The first study came out of New Zealand, that was Tomasina Stacey study in 2011. You can see that these studies have been conducted across the world, and no matter which study you look at, the findings are the same. They’re all pointing in the same direction.
The Cribss group have pooled the data from all of these studies into one big study which you can see here has got over 850 stillborn babies, and over 2000 live born babies involved. When all of that data is pooled and looked at in one study, what you can see here over on the far right, is that lying in a supine position or going to sleep in the supine position is associated with a two and a half times increase in odds of a stillborn baby. Or should I say having a stillborn baby is associated with two and a half times odds of having reported and going to sleep in the supine position.
There’s no real objective data. This is all done self-report. All of these studies on sleep position have been done with self-report. As important as that is, we now need to move forward and look at objective measures of sleep position. There is one study that was published in 2019 from the nuMoM2b study of about two and a half thousand pregnant women who had data available to look at this.
They measured sleep position one night in the first trimester, and one night in the second trimester, and didn’t find any association with stillbirth or small for gestational age, but actually that study doesn’t negate any of those previous findings because they didn’t do any monitoring in the third trimester, which is where all of the previous studies have been focused. I think what this study tells us is maybe supine sleep in early and mid-pregnancy is okay, and it’s the third trimester that we need to focus on.
Do we even know how much time pregnant women spend in the supine position? We’ve done a review of some in-lab sleep studies, which aren’t always the best, because it’s not your natural environment, wide range of gestational ages, as you can see, the average was about 28 weeks. We found that the majority of women actually spent at least sometime in the supine position, about 82% of women. The median proportion of supine sleep time was about a quarter of the night. That’s a good chunk of the night. That’s quite significant.
We’ve just finished a study looking at changes in sleep across pregnancy. This is where we enroll women in early pregnancy, we give them a home sleep study, and then we go back to them in the third trimester, we give them a home sleep study again, and we look at how sleep is changing across pregnancy. We’ve got about 170 women that have gone through both of these time points. What you can see here is in the blue, this is early pregnancy, on average, it was about 15 weeks. The purple is late pregnancy. It was about 35 and a half weeks by this point. You can see that sleep duration decreased, which is expected.
But the severity of the respiratory disturbance significantly increased. It went from about two events per hour to about five. The ODI is the oxygen desaturation index, so how many times per hour is somebody’s oxygen dropping. That significantly increased across pregnancy. Then the supine position, the average amount of time that women were spending supine was about 16% of the night in early pregnancy. That went up to about 22% of the night in late pregnancy.
When we looked at the proportion of women that had any supine sleep at all, it was about a third in early pregnancy, rising to about half of women by late pregnancy. Certainly, a significant proportion of women are spending quite a significant proportion of time on their back, and it seems to increase as pregnancy progresses.
There are disparities in these changes in sleep across pregnancy. You can see here where we have white women and we have Black women. You can see that the age of the Black women was younger. The Black women were younger, but they had higher BMIs at early pregnancy and higher BMI’s in late pregnancy compared to the white women. The white women in this graph are light blue in early pregnancy, dark blue in late pregnancy. The Black women are pink in early pregnancy and purple in late pregnancy.
I don’t have any significance in there because it would make it a very busy graph, but just to show you that the apnea hypopnea index increases like we saw on the previous slide as pregnancy progresses, but it increases more in the Black pregnant women than it did in the white. The same for the oxygen desaturation index. The changes were happening in the same direction for both of these races, but they were happening more in the Black women.
When we look at the supine position, we see the same thing. We see that more Black women had supine sleep in early pregnancy and it increased more in late pregnancy compared to the white women. What we’ve seen from this is that not only do Black pregnant women have poor sleep than white pregnant women, it appears to get worse as pregnancy progresses. The question on our minds now is do these changes play a role in the worst perinatal outcomes that are reported in Black women?
Other sleep practices related to stillbirth. This is the STARS study that was born at the inaugural stillbirth summit back in 2011. Many of you might be familiar with this. Our focus here on this case control arm, where we had 153 moms who’d had a stillborn baby within the last four weeks before filling out the survey and 488 mothers who’d had a live birth. We asked them about their sleep practices.
What we found was, in the mothers who had a stillborn baby, they were much more likely to have long sleep duration. More than nine hours sleep at night. They were much more likely to have non-restless sleep. That’s non-restless sleep. They were more likely to have very good sleep quality, and they were way more likely to not wake up very much. One time or less across the night, which all of these are counter-intuitive to what we may think.
When we thought about this, we thought, “Well, maybe there’s these long periods of undisturbed sleep that are risk factors for a stillborn baby. This is something that we really need to spend more time looking into.” We’ve now seen this in other studies buried in tables that have been reported, but not quite the main findings. This is not the only study to find this, but this is something that we really do need to focus on a little more.
What about the fetal behavioral states in certain maternal positions? This was a study by Peter Stone from New Zealand where they’d looked at fetal behavior. Quiet sleep, active sleep, active awake, in different maternal positions. You can see supine position here on the bottom. What they found was that in the supine position, the fetal heart rate variability was reduced, the fetal behavior change from an active behavior to a quiescence or a quiet state, and that’s a low oxygen consuming state.
In the presence of a stressor, and that stressor could be hypoxia, it could be poor perfusion, a shift to this low oxygen consuming state is actually protective. That’s what these babies seem to be doing when the mom was on her back. It may be that maternal supine position is not a good thing for fetal wellbeing and in compromised babies, so those with growth restriction, this particularly could be a sufficient enough stressor to contribute to the fetal demise.
This is a very new paper that just came out, again, from the New Zealand group. I thought this was a really nice figure to show you. Complicated, but I’ll just point out the key findings. This was an MRI study of 22 healthy pregnant women between 34 and 38 weeks. When they did the MRI studies, they compare the left lateral position to the supine position that the mother was in. They found that the supine position was associated with reduced uteroplacental blood flow, reduced oxygen transfer across the placenta, and you can see that the average reduction in fetal umbilical venous blood flow is 11%, and the average reduction in oxygen delivery to the fetus was 6%. Now, these are in healthy babies. It’d be really interesting to see whether these reductions are even higher in compromised babies. That’s some really exciting work that’s coming out again from New Zealand.
If sleep position does have this role in fetal health, then what can we do? Well, we can certainly intervene with sleep position, and we’ve done this in several studies now. This is showing very similar studies. One in Australia, one out of Canada. The top figures are showing that when we do this intervention– now this is the PrenaBelt. This is a belt that goes around the woman’s abdomen here, and you can see these little lumps in the back. It could be tennis balls, but they’re a solid ball that is uncomfortable if you lie on it. Women don’t want to lie on it.
You can put something very soft and collapsible in there so women think they’re in the intervention group, but they’re actually in a sham group. Nothing’s going to happen. They can still lay on their back and they’re not going to feel uncomfortable. That will be a control group. What you can see is that women in the control group have about an hour of supine sleep, but then when they were on the next night, when they wear this PrenaBelt, you can see that that’s reduced. The supine time is reduced by over half an hour. Similarly, when they use the intervention, they use this belt, the number of fetal heart rate decelerations now drops.
We found similar findings with the same device in Canada. You can see that in the sham, when they got those really soft squishy balls in there that do not change a woman’s position, about 16% of sleep time was on the back. When the intervention was active, so those balls were a little harder and people just would not lie on them because they’re not comfortable, the proportion of supine sleep went down to about three and a half percent of sleep time. Certainly, these interventions can work.
We’ve also done a very similar study in Ghana where we enrolled about 200 low-risk women. Again, it’s the same device. You can just see it from different angles here. What we found was that in the treatment group and the sham, the control group, number of nights use was the same, number of days in the trial was the same, adherence wasn’t very good. Only about 56% of women actually used it as we would like them to, but that’s often a problem with intervention trials.
We didn’t find any significant differences in birth weight, or birth centile, but the changes that we found were in the right direction. The babies in the treatment group were born a little bigger. You can see that birth weight is a little higher, and their centile is a little higher, although it didn’t quite reach statistical significance, but it’s certainly in the right direction. Women who had the active device also reduced their supine sleep time, and the proportion of babies born small for gestational age also reduced. Again, not quite statistically significant, but certainly in the right direction.
What’s next? Where do we go from here? We currently have an ongoing clinical trial that’s objectively monitoring sleep position across the third trimester. It’s with a little device here, the data goes up to the cloud and women are encouraged to wear it every night. We’re hoping to get some nice longitudinal data over the course of several months.
The goal is to enroll 500 women. This device has a vibration sensor in it, so women can be randomized to just observation mode or to the intervention mode. We’ve powered the study to determine if supine sleep is related to having a shorter gestation length and reduced birth weight. Like I said, this is an ongoing trial. We’ve currently got about 150 women enrolled. The average age so far is about 32, and the average gestation age is about 31 weeks. Unfortunately, I don’t have any results to share with you just yet because it’s an ongoing trial, but hopefully at the next stillbirth summit, we’ll be able to share those results with you. So watch this space.
With that, I will finish, and just tell you that maternal sleep is really important. It’s a significant contributor to maternal and fetal health, particularly gestational hypertension, preeclampsia, gestation diabetes, fetal growth problems, especially growth restriction, preterm birth, and of course, stillbirth. Interventions to optimize sleep in pregnant women may offer significant benefits to both mothers and babies. With that, I thank you for your attention.
Please feel free to ask questions of the presenter. We will obtain their answers/comments and provide them here as received.